Carotenoids are lipids which are soluble in organic solvents and can be extracted from tissues of plants and animals by polar solvents such as acetone and alcohols mixed with nonpolar solvents such as hexane, chloroform, ether, etc. Carotenoids are not directly soluble in water; in plants they are bonded in tissues and cells by fatty acids and oils and are present in colloid form with plant starches and polymers. Conventional methods of extraction and isolation of carotenoids are designed to separate carotenoid pigments from their natural protein starch complexes and from other plant pigments (such as porphyrins) and to isolate the carotenes separately. Use of organic solvents such as hexane, benzene, chloroform, acetone, ether and methanol or mixtures thereof for extraction of carotenoids from algae or other vegetables generally involves the removal of carotenoids from pulverized vegetable residues into the solvent, from which the carotenoids are then recovered by evaporation or distillation of the solvent. Various procedures have been developed to facilitate extraction of pure carotenoids.
In one method of extracting beta-carotene, for example, algae material is treated with calcium hydroxide and heated to a temperature of 50.degree. C. to about 100.degree. C. This results in conversion of chlorophyll present in the algae to calcium salts which are insoluble in the organic solvents used for beta-carotene extraction and as a result, chlorophyll pigments are absent from the final solvent extracted beta-carotene. See U.S. Pat. No. 4,439,629.
Efforts have also been directed toward providing water dispersible preparations of betacarotene. For example, a water dispersible preparation of beta-carotene has been prepared by adding beta-carotene to hot solutions of starch, then heating the mixture to temperatures of 100.degree.-121.degree. C. to stabilize the carotene. A food color with one absorption maxima of 520-530 nm can be made if pure synthetic betacarotene is used. See U.S. Pat. No. 3,790,688.
Beta-carotenoid in nature is always found associated with other pigments such as the tetrapyrroles and porphyrins (e.g., chlorophyll) and other carotenoids such as zeaxanthin and echinenone. Further, carotenes are present in membranes of animals and plants in carotenoid protein complexes called carotenoproteins. In conventional extraction procedures, these complexes are destroyed in the effort to obtain pure pigments.